Hours before dawn on Sunday morning, clocks across the nation sprang forward in their semi-annual ritual. Now that it has been a few years since Congress passed the Energy Policy Act of 2005, a bill that extended daylight savings for four weeks in order to save energy, do we know whether the law makers’ plan worked?

There are a few reports and studies that review the costs and benefits of changing daylight savings. One from the Department of Energy released last October states that there is an energy savings due to the change, about $500 million and 2.9 million barrels of oil to be exact, according to a government report.

The conclusions prompted authors of the bill like Representative Ed Markey from Massachusetts to say things like “government analysis has proven that extra sunshine provides more than just smiles,” and “Daylight Saving Time not only saves consumers money, but also curbs the nation’s energy consumption, while reducing carbon emissions that lead to global warming.”

Seemingly contradicting the government report is a study conducted by the University of California-Santa Barbara, which says that people in Indiana spent an extra $8.6 million when they adopted daylight savings in 2006, reported the Wall Street Journal (this article is free!).

A number of confounding factors, from agricultural productivity to safety, complicate the issue. It may take more than a handful of studies to light the way towards a brighter energy saving future.